Response to a code challenge to create a simple library system with the following requirements:
- Create libraries
- Create books
- Add different books to different libraries
- Find out if a library has a certain book, given the book's title
- Find out if a library has a certain book, given its ISBN number
- Find out if a library can get a book (by title or ISBN) through interlibrary loan from any of the other libraries you created
- Find out what a library's most popular book is (where popularity is measured by the number of times a user asked for that book; different libraries should have different answers to this question)
The code has been populated with sample data in order to fulfill and demonstrate the last requirement.